FIG. 14-113 Drag coefficient for flow past inclined flat plates for use in Eq. (14-228). [Calvert, Yung, and Leung, NTIS Puhl. PB-248050; based on Fage and Johansen, Proc. R. Soc. (London), 116A, 170 (1927).]
For widely spaced tubes, the target efficiency ng can be calculated from Fig. 17-39 or from the impaction data of Golovin and Putnam [Ind. Eng. Chem. Fundam., 1,264 (1962)]. The efficiency of the overall tube banks for a specific particle size can then be calculated from the equation n = 1 — (1 — nta'/A)n, where a is the cross-sectional area of all tubes in one row, A is the total flow area, and n is the number of rows of tubes.
Calvert reports pressure drop through tube banks to be largely unaffected by liquid loading and indicates that Grimison's correlations in Sec. 6 ("Tube Banks") for gas flow normal to tube banks or data for gas flow through heat-exchanger bundles can be used. However, the following equation is suggested:
where AP is cm of water; n is the number of rows of tubes; pg is the gas density, g/cm3; and Ug is the actual gas velocity between tubes in a row, cm/s. Calvert did find an increase in pressure drop of about 80 to 85 percent above that predicted by Eq. (14-230) in vertical upflow of gas through tube banks due to liquid holdup at gas velocities above 4 m/s.
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